IEEE 802.21 provides architecture to enable a seamless handover process based on measurements and triggers supplied from link layers. IEEE 802.21 defines media independent event service (ES), command service (CS) and information service (IS). IEEE 802.21 also defines medium access control (MAC) layer service access points (SAPs) and associated primitives for each specific access technology.
IEEE 802.21 MIH event and information service (EIS) requires MAC or physical layer-based event notification for link status updates between a user equipment (UE) and an MIH point of service (PoS). The MIH EIS events include link up, link down, link parameters change, link going down, service data unit (SDU) transmission status, link event rollback, pre trigger (L2 handoff imminent), and the like. Currently, link layer extensions required to support MIH EIS are under consideration for various technologies.
For Ethernet networks, link monitoring using continuity messages is necessitated where physical layer signaling is inadequate to detect a connectivity status between two communication peers. IEEE 802.3ah Ethernet first mile (EFM) provides an extension to the 802.3 physical layer signaling to facilitate a connectivity status determination. IEEE 802.3ah provides link monitoring, fault signaling and remote loopback. Link monitoring serves for detecting and indicating link faults under a variety of conditions so entities can detect failed and degraded connections. Fault signaling provides mechanisms for one entity to signal another that it has detected an error. Remote loopback, which is often used for troubleshooting, allows one entity to put another entity into a state whereby all inbound traffic is immediately reflected back onto the link.
IEEE 802.1ag, (also known as connectivity fault management (CFM)), specifies protocols, procedures and managed objects to support transport fault management for end to end Ethernet networks at the customer, operator and service provider levels. These allow discovery and verification of the path through bridges and local area networks (LANs) and detection and isolation of connectivity fault to a specific bridge or LAN.
CFM mechanisms for fault detection include continuity check, traceroute, loopback (ping), alarm indication, and the like, at different OAM domains, (e.g., operator domain, provider domain and customer domain). Each maintenance domain carries CFM messages using destination address and EtherType. CFM messages are sourced or received at maintenance end points (MEPs) after traversing zero or more maintenance intermediate points (MIPs). The CFM messages pass transparently through 802.1Q or 802.1ad bridges. Multiple instances of CFM can operate at multiple levels on the same bridge port simultaneously.
Although conventional arts provide a mechanism to detect link problems and provide this information to the link end-points, there is currently no means to make use of this information for the purpose of triggering handover operation towards an alternative link.